What does it mean to Write in the Spirit of Tolkien?

[Rumil]

At the risk of lowering the tone somewhat -

Tolkien seems to be devoid of the need of modern fantasy writers to explain everything. OK, I know you're thinking that he went to extreme lengths to fit everything into the mythology and language structure, but think in terms of geography.

We have no clue what is beyond Rhun, the appearence of the Variags (or even whether Balrogs have wings!) Of course, this infrormation wouldn't be known by the authors of the Red Book. He justifies the 'mystery' by the necessities of internal consistency. How would hobbits know anything about Far Harad after all? It's like the mediaeval maps which confidently stated 'here be dragons!' The snippets of information tantalise us !

In a related question, the style of Tolkiens wring (much pastiched) is surely 'copyable' (if that's a word) but woe betide those who reveal the mysteries, there wouldn't be anything left for us to discuss!